bug#55639: time-machine back in 2020: weird error

[Nicolò Balzarotti]

Hi, I think I'm experiencing the same issue.
I need opencv 3.4, found a commit with it 
(63856931dbe1e72311b472347331ce1c16b0de0b)

On two machines
> guix describe:
 guix eb87d2c

> guix describe:
 guix 59b102c

guix time-machine --commit=63856931dbe1e72311b472347331ce1c16b0de0b -- 
build opencv

Computing Guix derivation for 'x86_64-linux'... Backtrace:
          5-(primitive-load 
"/gnu/store/d5llsvv8g1idnm87q7cs4r5a4s0…")
In ice-9/eval.scm:
   155:9 4 (_ _)
   159:9 3 (_ #(#(#(#(#(#(#(#(#(#(#(…) …) …) …) …) …) …) 
…) …) …) …))
  173:47 2 (_ #(#(#(#(#(#(#(#(#(#(#(…) …) …) …) …) …) …) 
…) …) …) …))
In ./guix/self.scm:
   914:4 1 (guix-derivation "/gnu/store/hp2afllp9vsp4kmr67nrhr8ig…" 
…)
   885:2 0 (guile-for-build "3.0")

./guix/self.scm:885:2: In procedure guile-for-build:
Throw to key `match-error' with args `("match" "no matching pattern" 
"3.0")'.
guix time-machine: error: You found a bug: the program 
'/gnu/store/d5llsvv8g1idnm87q7cs4r5a4s0kxyap-compute-guix-derivation'
failed to compute the derivation for Guix (version: 
"63856931dbe1e72311b472347331ce1c16b0de0b"; system: "x86_64-linux";
host version: "59b102cab9d66ba0c561ed9ed8df04f9fc340bd2"; pull-version: 
1).
Please report it by email to <bug-guix@gnu.org>.


Same happens with --no-grafts, on both machines.

Any idea on what is causing it?

Thanks!